The invention generally relates to paper making systems and processes, and relates in particular, to systems and processes for facilitating the removal of fluids from papermaking material during paper making processes.
In the paper making process the press section is equipped with conveying belts commonly referred to as felts. The felts act to carry the newly formed, very wet paper to the pressing rolls where a considerable amount of water is forced out of the paper and into the felts. As these felts are serpentine in nature, it is necessary to remove the captured water from the felts so that the process of water removal from the paper is repeated as the continuous supply of newly form paper is processed through the press section.
The method presently in use today for water extraction from the serpentine felt involves the use of a vacuum element in the belt run commonly referred to as the fluid extraction box or Uhle box, which is typically constructed from a pipe or enclosure that has a contact wear surface attached to it. This contact wear surface incorporates within the design a through path for the vacuum applied water extraction stream to drain into. The vacuum applied to the felt is considerable and causes the felt to be pulled tightly onto the contact wear surface and into the vacuum port open area. This cover includes ports or pathways for the extracted water to be conveyed/evacuated to.
These vacuum application ports may be in various geometric configurations. Conventionally, the shape and open area of the port is sized for the vacuum exposure dwell time on the moving serpentine felt; dwell time that is too long wastes energy, too short does not allow enough time for the water to be fully extracted. Also, another design consideration is the slot (or opening) width, which has a direct correlation to felt wear and felt seam failure modes.
There remains a need however, for more efficient and effective systems for removing fluids from felts while minimizing wear on the felts.